1. Field of the Invention
The present invention relates to a method of producing moisture-permeable artificial leather and, more particularly, to a method of producing a moisture-permeable artificial leather comprising transferring a water-soluble inorganic salt-containing polyurethane layer onto a base fabric and washing the polyurethane layer with water to extract out said water-soluble inorganic salt.
2. Prior Art
Many different methods have been proposed for the production of moisture-permeable artificial leather. We previously developed a method of producing a moisture-permeable artificial leather comprising coating a surface-forming composition consisting of a one-component polyurethane, a water-soluble inorganic salt and an organic solvent on a release material, then evaporating the organic solvent from said composition, applying thereon a base fabric through an adhesive layer comprising a water-soluble inorganic salt, peeling off the release material from said surface layer and immersing the composite sheet in water to extract out the water-soluble inorganic salt from the two layers (Japanese Patent Kokai No. Sho-57-66186). We conducted a further study on the above method and found that the above surface layer-forming composition and adhesive layer-forming composition are mere admixtures of the water-soluble inorganic salt with the rest of the composition and, therefore, the water-soluble inorganic salt is not uniformly distributed in the compositions so that when the surface layer-forming composition is applied to the release material, streaks are produced in the surface layer to detract from the surface appearance of the product leather and the surface of the adhesive layer is also streaked to cause a decrease in adhesive strength. Furthermore, the resistance of the leather to flexure, abrasion, scratching, water and dry cleaning was also not as high as would be desired.
Aside from the foregoing, there is also known a moisture-permeable, water-proof coated fabric (Japanese Patent Kokai No. Sho-56-26076) having a microporous polyurethane skin layer at least on one side of a base fabric and possessing a water proofness of at least 700 mm H.sub.2 O/cm.sup.2 and a moisture permeability of at least 24 hours at 5000 g/m.sup.2. However, this prior art is a wet-coagulation system wherein the polyurethane layer coated on the base fabric is coagulated in water and the product obtainable thereby has the disadvantage of rough surface, inadequate flexibility, interlayer separation and poor color quality and is unsuited particularly for clothing purposes.
It is an object of this invention to provide an improved method over the technology for the production of artificial leather. More particularly, this invention provides an improved technology for manufacturing an artificial leather with improved surface qualities and increased resistance to flexure, abrasion, scratching, laundering and dry cleaning.